underboss vs assistant

underboss and assistant both are nouns.

Word	Noun	Adjective	Verb	Adverb
underboss	Yes	No	No	No
assistant	Yes	Yes	No	No

As nouns, assistant is a hypernym of underboss; that is, assistant is a word with a broader meaning than underboss:

underboss: an assistant or second-in-command to a chief (especially in a crime syndicate)
assistant: a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

Other hypernyms of underboss include help, helper, supporter.

underboss (noun)	assistant (noun)
an assistant or second-in-command to a chief (especially in a crime syndicate)	a person who contributes to the fulfillment of a need or furtherance of an effort or purpose

underboss (adjective)	assistant (adjective)
	of or relating to a person who is subordinate to another